Something to think about: The original meaning of the English word 'want', going back to its roots in Old Norse, was 'lack'. Over time, it came to mean 'need' ( given that if you were lacking something, you needed to have it) and only much later did 'want' acquire its modern sense of 'desire'. You'll occasionally come across this original meaning of 'want' even today: for example, in the slightly old-fashioned phrases "for want of" (meaning 'because of the lack of') or "he wanted for nothing" (meaning that he had everything he needed). So when we say "It's cold in Berlin in January. You'll want a warm coat" we are indeed using 'want' to mean 'need' ( rather than 'desire'). It's an informal usage, but one which actually predates the modern meaning of the word.

Want is about preference or desire, need is about necessity. I want a million dollars; it will make my life easier. I need oxygen; if I don't have any, I will die. In English, we'll often use "need" for something that is wanted a lot or to stress the importance of a thing. ("We really need a good grocery store in this town.") But, we also often ask people questions like "Do you really _need_ that? Or do you just want it?" and "Is that really a _need_?" so that we can clarify what the speaker's actual intent was. So, the two words are not entirely interchangeable. You can use "need" instead of "want" in some circumstances and someone might question your word choice.

Hi... I think “NEED” would be grammatically the right option. Also “NEED” you can use it in a formal conversation, or as a suggestion. Yet WANT people use it more in an informal conversation between two friends for instance. For instance you tell your best friend... “Come on bro in order to make a good impression you also want a good suit”. Like telling him that if he doesn’t use a suit, he won’t make a good impression. Like “is obvious”. That’s my opinion. Depends on contest.

'want' is used more if you desire something. But 'need' is used more if you have a necessity for it (it's important!), based on external circumstances. For the example you mention, I would use 'need' because you are talking more in general and making a recommendation. In order to make a good impression you 'need' a good suit (it's important to have one). However, if it was more personal you could use want, e.g. I 'want' a new suit to make a good impression at job interviews.